Electrical Properties of Ga2O3 Schottky Barrier Diodes with and without Mesa Structure

Devices based on wide bandgap (WBG) semiconductors like silicon carbide (SiC), gallium nitride (GaN), and gallium oxide (Ga 2 O 3 ) are ideal for high-power electronics in harsh environments. Among the WBG semiconductors, ultrawide bandgap (UWBG) β-phase gallium oxide (Ga 2 O 3 ), E G ≈ 4.8 eV, is emerging as a replacement for the current commercially available wide bandgap (WBG) power electronics due to its generational improvements in performance and manufacturing cost [1]. Ga 2 O 3 has a high theoretical breakdown electrical field of 8 MV/cm which in turn gives its Baliga’s figure of merit for power devices that is larger than other WBG materials. The availability of high-quality Ga 2 O 3 substrates produced from melt-grown bulk single crystals also facilitates the development of vertical power devices. In the current stage, the vertical Schottky barrier diode (SBD) with Ga 2 O 3 can have an improved current spreading effect when compared to power diode devices from Si, SiC, and GaN. Especially, the Ga 2 O 3 is expected to surpass the trade-off relationship between breakdown voltage (BV) and on resistance (R on,sp ) that other materials have [2]. Nevertheless, the Ga 2 O 3 vertical SBD still cannot achieve the theoretical breakdown electric field. One of the key topics for WBG semiconductors application is a structure for improved electrical management such as field rings, junction termination extension, and field plates to reduce the leakage current in the reverse bias state. Here, we investigate the characteristics of Ga 2 O 3 SBDs with and without mesa structure in extreme environments at high and low temperature. Conventional and mesa Ga 2 O 3 SBDs were fabricated on the halide vapor phase epitaxy (HVPE) grown β-Ga 2 O 3 (001). A Sn-doped substrate with 610 16 cm -3 was used for the HVPE growth. In the SBD with mesa structure, the circular mesa with a diameter of 162 μm and a depth of 500 nm was formed around anode electrodes. The Ti/Au metal stack on the back side of the substrate acted as a cathode and the anode electrode deposited Ni/Au/Pt layers. After the fabrication process, current-voltage (I-V) measurements were performed on the SBDs between -5 V and 1 V. From the results, the values of R on,sp at 0.7 V are 46.4 Ω•cm 2 and 46.2 Ω•cm 2 in conventional and mesa SBDs, respectively. And additionally, the leakage current at -5 V is reduced by approximately 44.3% in the mesa structure. To obtain the Schottky barrier height (SBH) from I-V and capacitance-voltage (C-V) measurements, the C-V was observed in the range of -5 V to 0.5 V at 100 kHz. The SBH values from I-V and C-V measurements, the mesa SBDs have 1% - 5% larger SBH compared to the conventional structure, and it could be related to lower leakage current. Moreover, the depletion depths of conventional and mesa SBDs were 52.2 nm and 57.8 nm, respectively, from C-V measurements. For considering the electrical characteristics in extreme temperatures, the I-V measurements of both SBDs structure will be measured between 75 K to 525 K. From an initial low temperature measurement series, we determine a Richardson constant of 49 A/cm 2 comparable to what has been reported by other groups. Furthermore, we will extend the study by performing deep-level transient spectroscopy (DLTS) to understand the defect information in Ga 2 O 3 . References [1] Pearton, S. J., Yang, J., Cary IV, P. H., Ren, F., Kim, J., Tadjer, M. J., & Mastro, M. A. (2018). A review of Ga2O3 materials, processing, and devices. Applied Physics Reviews , 5 (1), 011301. [2] Higashiwaki, M., Sasaki, K., Murakami, H., Kumagai, Y., Koukitu, A., Kuramata, A., ... & Yamakoshi, S. (2016). Recent progress in Ga2O3 power devices. Semiconductor Science and Technology , 31 (3), 034001.